Nonvolatile memory device and method of manufacturing the same

ABSTRACT

A nonvolatile memory device having a vertical structure and a method of manufacturing the same, the nonvolatile memory device including a channel region that vertically extends from a substrate; gate electrodes on the substrate, the gate electrodes being disposed along an outer side wall of the channel region and spaced apart from one another; and a channel pad that extends from one side of the channel region to an outside of the channel region, the channel pad covering a top surface of the channel region.

CROSS-REFERENCE TO RELATED APPLICATIONS

Korean Patent Application No. 10-2011-0021042, filed on Mar. 9, 2011, inthe Korean Intellectual Property Office, and entitled: “NonvolatileMemory Device and Method of Manufacturing the Same,” is incorporated byreference herein in its entirety.

BACKGROUND

1. Field

Embodiments relate to a nonvolatile memory device and a method ofmanufacturing the same.

2. Description of the Related Art

Sizes of electronic products should be minimized and the devices shouldprocess more data. Accordingly, it may be necessary to increase a degreeof integration of semiconductor memory devices used in such electronicproducts. In order to increase the degree of integration ofsemiconductor memory devices, nonvolatile memory devices having avertical transistor structure, instead of a planar transistor structure,have been considered.

SUMMARY

Embodiments are directed to a nonvolatile memory device and a method ofmanufacturing the same.

The embodiments may be realized by providing a nonvolatile memory devicehaving a vertical structure, the nonvolatile memory device including achannel region that vertically extends from a substrate; gate electrodeson the substrate, the gate electrodes being disposed along an outer sidewall of the channel region and spaced apart from one another; and achannel pad that extends from one side of the channel region to anoutside of the channel region, the channel pad covering a top surface ofthe channel region.

The channel pad may include a channel extending portion verticallyextending on the channel region, and a spacer on an outercircumferential surface of the channel extending portion.

The nonvolatile memory device may further include a buried insulatinglayer at a center of the channel region, wherein the channel pad furtherincludes a conductive layer on a top surface of the buried insulatinglayer, the conductive layer filling in the channel extending portion.

A distance between the substrate and a bottom surface of the conductivelayer may be less than a distance between the substrate and a bottomsurface of the spacer.

The spacer may form a bent portion at a boundary with an outer side wallof the channel extending portion or the channel region.

An area of a top surface of the channel pad may be greater than an areaof the top surface of the channel region.

The nonvolatile memory device may further include a bit line contactplug on the channel pad, the bit line contact plug being connected to abit line.

The nonvolatile memory device may further include an insulating spaceron a side surface of the channel pad.

The channel pad may include a channel extending portion verticallyextending on the channel region, and a cover portion on the channelextending portion, the cover portion having an area greater than an areaof the channel extending portion.

The embodiments may also be realized by providing a method ofmanufacturing a nonvolatile memory device having a vertical structure,the method including alternately stacking interlayer sacrificial layersand interlayer insulating layers on a substrate; forming first openingsthat pass through the interlayer sacrificial layers and the interlayerinsulating layers and exposing the substrate; forming a channel regionover each of the first openings; and forming a channel pad that extendsfrom the first opening to an outside of the channel region to cover atop surface of the channel region.

Forming the channel pad may include forming a channel extending portionon the channel region at an upper part of each of the first openings,forming a conductive layer in each of the first openings such that theconductive layer is connected to the channel extending portion; removingportions of the interlayer insulating layers at a side surface of thechannel extending portion to a predetermined height to expose the sidesurface of the channel extending portion; and forming a conductivespacer on the side surface of the channel extending portion.

A first distance between the substrate and a bottom surface of theconductive layer may be less than a second distance between thesubstrate and a bottom surface of the conductive spacer.

The method may further include forming a buried insulating layer on thechannel region to fill each of the first openings after forming thechannel region, wherein the conductive layer is formed on a top surfaceof the buried insulating layer.

The method may further include forming an insulating spacer on a sidesurface of the channel pad after forming the channel pad.

Forming the channel pad may include depositing a conductive material ona top surface of the channel region; and patterning the conductivematerial by photolithography.

The embodiments may also be realized by providing a nonvolatile memorydevice having a vertical structure, the nonvolatile memory deviceincluding a channel region that vertically extends from a substrate;gate electrodes on the substrate, the gate electrodes being disposedalong an outer side wall of the channel region and spaced apart from oneanother; and a conductive channel pad on and electrically connected tothe channel region, wherein the channel pad covers a top surface of thechannel region, and an area of a top surface of the channel pad isgreater than an area of a top surface of the channel region.

The channel pad may include a conductive channel extending portionoverlying the channel region, a conductive layer encompassed by thechannel extending portion, and a conductive spacer on an outercircumferential surface of the channel extending portion.

The nonvolatile memory device may further include an insulating spaceron an outer circumferential surface of the channel pad.

The channel pad may include a conductive channel extending portionoverlying the channel region, a conductive layer encompassed by thechannel extending portion, and a conductive cover portion overlying thechannel extending portion and the conductive layer, an area of a topsurface of the cover portion being greater than an area of top surfacesof the channel extending portion and the conductive layer.

The nonvolatile memory device may further include a bit line contactplug on and electrically connected to the channel pad, the bit linecontact plug being electrically connected to a bit line.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will become apparent to those of ordinary skill in theart by describing in detail exemplary embodiments with reference to theattached drawings, in which:

FIG. 1 illustrates an equivalent circuit of a memory cell array of anonvolatile memory device according to an embodiment;

FIG. 2 illustrates an equivalent circuit of a memory cell string of anonvolatile memory device according to another embodiment;

FIG. 3 illustrates a perspective view of a three-dimensional (3D)structure of memory cell strings of a nonvolatile memory deviceaccording to an embodiment;

FIG. 4A illustrates an enlarged cross-sectional view of a gatedielectric film of the structure of FIG. 3 according to an embodiment;

FIG. 4B illustrates an enlarged view of the gate dielectric film of thestructure of FIG. 3 according to another embodiment;

FIGS. 5A through 5N illustrate cross-sectional views of stages in amethod of manufacturing the nonvolatile memory device of FIG. 3;

FIG. 6 illustrates a perspective view of a 3D structure of memory cellstrings of a nonvolatile memory device according to another embodiment;

FIGS. 7A through 7G illustrate cross-sectional views of stages in amethod of manufacturing the nonvolatile memory device of FIG. 6;

FIG. 8 illustrates a perspective view of a 3D structure of memory cellstrings of a nonvolatile memory device according to yet anotherembodiment; and

FIGS. 9A through 9C illustrate cross-sectional views of stages in amethod of manufacturing the nonvolatile memory device of FIG. 8; and

FIG. 10 illustrates a block diagram of a nonvolatile memory deviceaccording to an embodiment.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. It will also be understood thatwhen a layer or element is referred to as being “on” another layer orsubstrate, it can be directly on the other layer or substrate, orintervening layers may also be present. Further, it will be understoodthat when a layer is referred to as being “under” another layer, it canbe directly under, and one or more intervening layers may also bepresent. In addition, it will also be understood that when a layer isreferred to as being “between” two layers, it can be the only layerbetween the two layers, or one or more intervening layers may also bepresent. Like reference numerals refer to like elements throughout.

Variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, exemplary embodiments should not be construed as limitedto the particular shapes of regions illustrated herein but may be toinclude deviations in shapes that result, for example, frommanufacturing. Like reference numerals denote like elements.Furthermore, various elements and regions illustrated in the drawingsare schematic in nature and their shapes may not be intended toillustrate the actual shapes of the elements or the regions and may notbe intended to limit the scope of the exemplary embodiments.

FIG. 1 illustrates an equivalent circuit of a memory cell array 10 of anonvolatile memory device according to an embodiment. In FIG. 1, anequivalent circuit of a NAND flash memory device having a verticalchannel structure is illustrated.

Referring to FIG. 1, the memory cell array 10 may include a plurality ofmemory cell strings 11. Each of the memory cell strings 11 may have avertical structure that extends in a vertical direction (i.e., az-direction) perpendicular to directions (i.e., an x-direction and ay-direction) in which a main surface of a substrate (not shown) extends.The plurality of memory cell strings 11 may constitute a memory cellblock 13.

Each of the memory cell strings 11 may include a plurality of memorycells MC1 through MCn, a string selection transistor SST, and a groundselection transistor GST. In each of the memory cell strings 11, theground selection transistor GST, the plurality of memory cells MC1through MCn, and the string selection transistor SST may be arranged inseries in the vertical direction (i.e., the z-direction). The pluralityof memory cells MC1 through MCn may store data. A plurality of wordlines WL1 through WLn may be respectively connected to the memory cellsMC1 through MCn to control the memory cells MC1 through MCn. The numberof memory cells MC1 through MCn may be appropriately determinedaccording to a desired capacity of the nonvolatile memory device.

A plurality of bit lines BL1 through BLm (extending in the x-direction)may be connected to one end of respective memory cell strings 11arranged in first through mth columns of the memory cell block 13, e.g.,drains of the string selection transistors SST. Also, a common sourceline CSL may be connected to another end of respective memory cellstrings 11, e.g., sources of the ground selection transistors GST.

The word lines WL1 through WLn (extending in the y-direction) may becommonly connected to gates of respective memory cells MC1 through MCn.Data of the plurality of memory cells MC1 through MCn may be programmed,read, or erased according to operations of the word lines WL1 throughWLn.

In the memory cell strings 11, the string selection transistors SST maybe disposed between the bit lines BL1 through BLm and the memory cellsMC1 through MCn. In the memory cell block 13, the string selectiontransistors SST may control data transfer between the plurality of bitlines BL1 through BLm and the plurality of memory cells MC1 through MCnusing string selection lines SSL connected to gates of the stringselection transistors SST.

The ground selection transistors GST may be disposed between theplurality of memory cells MC1 through MCn and the common source lineCSL. In the memory cell block 13, the ground selection transistors GSTmay control data transfer between the plurality of memory cells MC1through MCn and the common source line CSL due to ground selection linesGSL being connected to gates of the ground selection transistors GST.

FIG. 2 illustrates an equivalent circuit of a memory cell string of anonvolatile memory device according to another embodiment. In FIG. 2, anequivalent circuit of one memory cell string 11A included in a NANDflash memory device having a vertical channel structure is illustrated.

In FIG. 2, the same elements as those in FIG. 1 are denoted by the samereference numerals, and a repeated detailed explanation thereof isomitted.

While the string selection transistor SST may be a single transistor inFIG. 1, a pair of string selection transistors SST1 and SST2, instead ofthe string selection transistor SST of FIG. 1, may be arranged in seriesbetween a bit line BL and the memory cells MC1 through MCn in FIG. 2. Inthis case, a string selection line SSL may be commonly connected togates of the string selection transistors SST1 and SST2. The stringselection line SSL may correspond to a first string selection line SSL1or a second string selection line SSL2 of FIG. 1.

Also, while the ground selection transistor GST is a single transistorin FIG. 1, a pair of ground selection transistor GST1 and GST2, insteadof the ground selection transistor GST, may be arranged in seriesbetween the plurality of memory cells MC1 through MCn and the commonsource line CSL in FIG. 2. In this case, the ground selection line GSLmay be commonly connected to gates of the ground selection transistorsGST1 and GST2. The ground selection line GSL may correspond to a firstground selection line GSL1 or a second ground selection line GSL2 ofFIG. 1.

The bit line BL may correspond to any one of the bit lines BL1 throughBLm of FIG. 1.

FIG. 3 illustrates a perspective view of a three-dimensional (3D)structure of memory cell strings of a nonvolatile memory device 1000according to an embodiment.

In FIG. 3, some elements constituting the memory cell string 11 of FIG.1 may not be shown. For example, the bit lines BL2 through BLm of thememory cell string 11 are not shown.

Referring to FIG. 3, the nonvolatile memory device 1000 may includechannel regions 120 on a substrate 100 and a plurality of memory cellstrings along side walls of the channel regions 120. The plurality ofmemory cell strings may extend in the y-direction along side surfaces ofthe channel regions 120 (that are arranged in the y-direction). As shownin FIG. 3, the memory cell strings 11 or 11A (see FIGS. 1 and 2)extending in a z-direction from the substrate 100 may be arranged alongthe side surfaces of the channel regions 120. Each of the memory cellstrings 11 or 11A may include two ground selection transistors GST1 andGST2, a plurality of memory cells MC1, MC2, MC3, and MC4, and two stringselection transistors SST1 and SST2.

The substrate 100 may have a main surface that extends in a plane of thex-direction and the y-direction. The substrate 100 may include asemiconductor material, e.g., a group IV semiconductor, a group III-Vcompound semiconductor, or a group II-VI oxide semiconductor. Forexample, the group IV semiconductor may include silicon, germanium, orsilicon-germanium. In an implementation, the substrate 100 may be a bulkwafer or an epitaxial layer.

The channel regions 120 (each having a pillar shape) may be disposed onthe substrate 100 to extend in the z-direction. The channel regions 120may be disposed apart from one another in the x- and y-directions in azigzag fashion along the y-direction. For example, the plurality ofchannel regions 120 adjacent to one another in the y-direction may beoffset in the x-direction. Also, although the channel regions 120 areoffset in 2 columns in FIG. 3, the embodiments are not limited thereto,and the channel regions 120 may be disposed in a zigzag fashion to beoffset in 3 or more columns. The channel regions 120 may be formed tohave annular shapes. Bottom surfaces of the channel regions 120 maydirectly contact the substrate 100 and thus, the channel regions 120 maybe electrically connected to the substrate 100. The channel regions 120may include a semiconductor material, e.g., polysilicon or singlecrystal silicon, and the semiconductor material may be undoped, or mayinclude, e.g., p-type or n-type impurities. A buried insulating layer130 may be formed in each of the channel regions 120. Although thechannel regions 120 adjacent to each other with a common source line 107therebetween are illustrated as being symmetric to each other about thecommon source line 107 in FIG. 3, the embodiments are not limitedthereto.

A channel pad 170 may cover a top surface of the buried insulating layer130 and may be electrically connected to respective ones of the channelregions 120. The channel pad 170 may include a conductive layer 172 (onthe top surface of the buried insulating layer 130), a channel extendingportion 174 (on or overlying the channel region 120 or formed when thechannel region 120 extends around the conductive layer 172), and aspacer 176 (disposed around the channel extending portion 174). In animplementation, the channel extending portion 174 and the conductivelayer 172 may be integrally formed. The conductive layer 172 may beencompassed by the channel extending portion 174. The channel extendingportion may be formed of a conductive material. A distance between thesubstrate 100 and a bottom surface of the spacer 176 may be greater thana distance between the substrate 100 and a bottom surface of theconductive layer 172. However, relative lengths of the conductive layer172 and the spacer 176 are not limited thereto, and may change invarious ways.

A bit line contact plug (not shown) may be connected to the channel pad170. The channel pad 170 may act as drain regions of the stringselection transistors SST1 and SST2. Due to the spacer 176, an area of aregion to which the bit line contact plug is connected may be a secondarea S2, which may be greater than an area S1, as illustrated in FIG. 3.

The channel pad 170 may include a conductive material, e.g., polysiliconand/or a metal. The conductive layer 172, the channel extending portion174, and the spacer 176 may include the same material or differentmaterials. In an implementation, only the conductive layer 172 and thechannel extending portion 174 may be formed of the same material.

A plurality of the first string selection transistors SST1 arranged inthe x-direction may be commonly connected to the bit lines BL (see FIG.2) via the channel pads 170. The bit lines BL may extend in a linearpattern in the x-direction, and the first string selection transistorsSST1 may be electrically connected to the bit line contact plugs formedon the channel pads 170. Also, a plurality of the first ground selectiontransistors GST1 arranged in the x-direction may be electricallyconnected to impurity regions 105 adjacent to the first ground selectiontransistors GST1.

The impurity regions 105 may be arranged adjacent to the main surface ofthe substrate 100 to extend in the y-direction and to be spaced apartfrom one another in the x-direction. One impurity region 105 may bedisposed between two channel regions 120 in the x-direction. Theimpurity regions 105 may be source regions, and may form a PN junctionwith others regions of the substrate 100. The impurity regions 105 mayinclude high density impurity regions (not shown) that are disposedadjacent to the main surface of the substrate 100 and located at acenter of the impurity region 105, and low density impurity regions (notshown) that are disposed at sides of the high density impurity regions.

The common source line 107 may be disposed on each of the impurityregions 105 to extend in the z-direction and to be in ohmic contact withthe impurity region 105. The common source line 107 may provide sourceregions to the ground selection transistors GST1 and GST2 of memory cellstrings of side surfaces of two channel regions 120 that are adjacent toeach other in the x-direction. The common source line 107 may extend inthe y-direction along the impurity region 105. The common source line107 may include a conductive material. For example, the common sourceline 107 may include at least one metal material selected from tungsten(W), aluminum (Al), and copper (Cu). Although not shown in FIG. 3, asilicide layer may be interposed between the impurity region 105 and thecommon source line 107 in order to reduce contact resistance. Thesilicide layer (not shown) may include a metal silicide layer, e.g., acobalt silicide layer. Insulating regions 185 having spacer shapes maybe formed on side surfaces of the common source line 107.

A plurality of gate electrodes 151 through 158 (which are collectivelyreferred to as gate electrodes 150) may be arranged along the sidesurface of the channel region 120 and spaced apart from the substrate100 in the z-direction. The gate electrodes 150 may be gates of theground selection transistors GST1 and GST2, the plurality of memorycells MC1, MC2, MC3, and MC4, and the string selection transistors SST1and SST2. The gate electrodes 150 may be commonly connected to adjacentmemory cell strings arranged in the y-direction. The gate electrodes 157and 158 of the string selection transistors SST1 and SST2 may beconnected to the string selection line SSL (see FIG. 1). The gateelectrodes 153, 154, 155, and 156 of the memory cells MC1, MC2, MC3, andMC4 may be connected to the word lines WL, WL2, WLn-1, and WLn (seeFIGS. 1 and 2), respectively. The gate electrodes 151 and 152 of theground selection transistors GST1 and GST2 may be connected to theground selection line GSL (see FIG. 1). The gate electrodes 150 mayinclude a metal film, e.g., a tungsten (W) film. Also, although notshown in FIG. 3, the gate electrodes 150 may further include a diffusionbarrier film. For example, the diffusion barrier film may include anyone selected from the group of tungsten nitride (WN), tantalum nitride(TaN), and titanium nitride (TiN).

A gate dielectric film 140 may be disposed between the channel region120 and the gate electrodes 150. Although not shown in detail in FIG. 3,the gate dielectric film 140 may include a tunneling insulating layer, acharge storage layer, and a blocking insulating layer (which aresequentially stacked from the channel region 120).

The tunneling insulating layer may tunnel charges to the charge storagelayer by using F-N tunneling. The tunneling insulating layer mayinclude, e.g., a silicon oxide. The charge storage layer may be a chargetrap layer or a floating gate conductive film. For example, the chargestorage layer may include quantum dots or nanocrystals. In animplementation, the quantum dots or the nanocrystals may includeconductors, e.g., metal or semiconductor particles. The blockinginsulating layer may include a high-k dielectric material. In animplementation, the high-k dielectric material may refer to a dielectricmaterial having a dielectric constant higher than that of an oxide film,e.g., a silicon oxide film.

A plurality of interlayer insulating layers 161 through 169 (which arecollectively referred to as interlayer insulating layers 160) may bearranged between the gate electrodes 150. The interlayer insulatinglayers 160 may be spaced apart from one another in the z-direction andmay extend in the y-direction, like the gate electrodes 150. One sidesurface of the interlayer insulating layers 160 may contact the channelregions 120. The interlayer insulating layers 160 may include, e.g.,silicon oxide or silicon nitride.

Although four memory cells MC1, MC2, MC3, and MC4 are arranged in FIG.3, the embodiments are not limited thereto, and more or fewer memorycells may be arranged according to a desired capacity of thesemiconductor memory device 1000. Also, two string selection transistorsSST1 and SST2 and two ground selection transistors GST1 and GST2 of thememory cell strings may be arranged. Gate lengths of the (selection)gate electrodes 151, 152, 157, and 158 when the number string selectiontransistors SST and ground selection transistors GST is at least two maybe much lower than gate lengths of the (selection) gate electrodes 151,152, 157, and 158 when the number of string selection transistors SSTand ground selection transistors GST is one, thereby facilitatingfilling between the interlayer insulating layers 160 without voids.However, the embodiments are not limited thereto, and a memory cellstring may include only one string selection transistor SST and oneground selection transistor GST as shown in FIG. 1. Also, the stringselection transistor SST and the ground selection transistor GST mayhave structures different from those of the memory cells MC1, MC2, MC3,and MC4.

In the nonvolatile memory device 1000 having a vertical structure ofFIG. 3, an area of, e.g., an upper surface of, the channel pad 170 (towhich a bit line contact plug for connecting the channel region 120 anda bit line is connected) may be greater than an area of the channelregion 120. For example, the area of the channel pad 170 (to which a bitline contact plug for connecting the channel region 120 and a bit lineis connected) may be greater than a sectional area of the channel region120. Accordingly, although a size of the channel region 120 may decreaseas the nonvolatile memory device 1000 is minimized, the bit line contactplug may be stably formed.

FIG. 4A illustrates an enlarged cross-sectional view of a portion A ofFIG. 3, showing the gate dielectric film 140 according to an embodiment.FIG. 4B illustrates an enlarged view showing the gate dielectric film140 according to another embodiment.

Referring to FIG. 4A, the channel region 120 may be used as a channel ofa memory cell string. The buried insulating layer 130 may be disposed onone side, e.g., a left side, of the channel region 120. The gatedielectric film 140 may be disposed on another side, e.g., a right side,of the channel region 120. Also, the interlayer insulating layers 160may contact one, e.g., a right, side wall of the channel region 120 andmay be disposed over and under the gate dielectric film 140. The gatedielectric film 140 may be disposed to cover one, e.g., a right, sidesurface of an upper interlayer insulating layer 160, to surround thegate electrodes 150, and to cover one, e.g., a right, side surface of alower interlayer insulating layer 160, thereby forming one surface. Theinsulating region 185 may be located on sides, e.g., right sides, of thegate electrodes 150 and the gate dielectric film 140.

The gate dielectric film 140 may include a tunneling insulating layer142, a charge storage layer 144, and a blocking insulating layer 146,which may be sequentially stacked from one, e.g., a right, side wall ofthe channel region 120.

The tunneling insulating layer 142 may be a single layer or amulti-layer structure including at least one of silicon oxide (SiO₂),silicon nitride (Si₃N₄), silicon oxynitride (SiON), hafnium oxide(HfO₂), hafnium silicon oxide (HfSi_(x)O_(y)), aluminum oxide (Al₂O₃),and zirconium oxide (ZrO₂).

The charge storage layer 144 may be a charge trap layer or a floatinggate conductive film. If the charge storage layer 142 is a floating gateconductive film, the charge storage layer 144 may be formed bydepositing polysilicon by using chemical vapor deposition (CVD), e.g.,low pressure CVD (LPCVD) using SiH₄ gas or Si₂H₆ and PH₃ gas. If thecharge storage layer 144 is a charge trap layer, the charge storagelayer 144 may include at least one of silicon oxide (SiO₂), siliconnitride (Si₃N₄), silicon oxynitride (SiON), hafnium oxide (HfO₂),zirconium oxide (ZrO₂), tantalum oxide (Ta₂O₃), titanium oxide (TiO₂),hafnium aluminum oxide (HfAl_(x)O_(y)), hafnium tantalum oxide(HfTa_(x)O_(y)), hafnium silicon oxide (HfSi_(x)O_(y)), aluminum nitride(Al_(x)N_(y)), and aluminum gallium nitride (AlGa_(x)N_(y)).

The blocking insulating layer 146 may include at least one of siliconoxide (SiO₂), silicon nitride (Si₃N₄), silicon oxynitride (SiON), and ahigh-k dielectric layer. The blocking insulating layer 146 may be formedof a material having a dielectric constant higher than that of thetunneling insulating layer 142. The high-k dielectric layer may includeat least one of aluminum oxide (Al₂O₃), tantalum oxide (Ta₂O₃), titaniumoxide (TiO₂), yttrium oxide (Y₂O₃), zirconium oxide (ZrO₂), zirconiumsilicon oxide (ZrSi_(x)O_(y)), hafnium oxide (HfO₂), hafnium siliconoxide (HfSi_(x)O_(y)), lanthanum oxide (La₂O₃), lanthanum aluminum oxide(LaAl_(x)O_(y)), lanthanum hafnium oxide (LaHf_(x)O_(y)), hafniumaluminum oxide (HfAl_(x)O_(y)), and praseodymium oxide (Pr₂O₃).

Referring to FIG. 4B, a buried insulating layer 230 may be disposed onone, e.g., a left, side of the channel region 220. A gate dielectricfilm 240 may cover an entire, e.g., right, side surface of a channelregion 220. Also, a gate electrode 250 may be disposed on one, e.g., aright, side of the gate dielectric film 240. Interlayer insulatinglayers 260 may be disposed over and under the gate electrode 250, and aninsulating region 285 may be disposed on one, e.g., a right, side of thegate electrode 250.

The gate dielectric film 240 may include a tunneling insulating layer242, a charge storage layer 244, and a blocking insulating layer 246,which may be sequentially stacked from one, e.g., a right, side wall ofthe channel region 220. The tunneling insulating layer 242, the chargestorage layer 244, and the blocking insulating layer 246 may besubstantially the same as the tunneling insulating layer 142, the chargestorage layer 144, and the blocking insulating layer 146 of FIG. 4A,respectively.

FIGS. 5A through 5N illustrate cross-sectional views showing stages in amethod of manufacturing the nonvolatile memory device of FIG. 3, whenseen in the y-direction.

Referring to FIG. 5A, interlayer sacrificial layers 111 through 118(which are collectively referred to as interlayer sacrificial layers110) and the plurality of interlayer insulating layers 161 through 169(which are collectively referred to as the interlayer insulating layers160) may be alternately stacked on the substrate 100. The interlayersacrificial layers 110 and the interlayer insulating layers 160 may bealternately stacked on the substrate 100 starting with or from theinterlayer insulating layer 161. The interlayer sacrificial layers 110may be formed of a material having an etch selectivity with respect tothe interlayer insulating layers 160. For example, the interlayersacrificial layers 110 may be formed of a material that allows theinterlayer sacrificial layers 110 to be etched while minimizing etchingof the interlayer insulating layers 160. An etch selectivity may referto a ratio of a rate at which the interlayer insulating layers 160 areetched to a rate at which the interlayer sacrificial layers 110 areetched. For example, the interlayer insulating layers 160 may be formedof at least one of a silicon oxide film and a silicon nitride film, andthe interlayer sacrificial layers 110 may be formed of a film selectedfrom the group of a silicon film, a silicon oxide film, a siliconcarbide film, and a silicon nitride film, which is different from thatof the interlayer insulating films 160.

According to the present embodiment, as shown in FIG. 5A, thicknesses ofthe interlayer insulating layers 160 may not be the same. The interlayerinsulating layer 161 (that is a lowermost layer of the interlayerinsulating layers 160) may have a relatively small thickness. Theinterlayer insulating layer 169 (that is an uppermost layer of theinterlayer insulating layers 160) may have a relatively large thickness.However, thicknesses of the interlayer insulating layers 160 and theinterlayer sacrificial layers 110 may differ, and the number of layersconstituting each of the interlayer insulating layers 160 and theinterlayer sacrificial layers 110 may also vary.

Referring to FIG. 5B, first openings Ta may be formed through thealternately stacked interlayer insulating layers 160 and the interlayersacrificial layers 110. The first openings Ta may be holes having adepth in the z-direction. Also, adjacent first openings Ta may beisolated and may be spaced apart in the x-direction and the y-direction(see FIG. 3).

The first openings Ta may be formed by forming a predetermined maskpattern (not shown) that defines locations of the first openings Ta inthe alternately stacked interlayer insulating layers 160 and theinterlayer sacrificial layers 110, and anisotropically etching theinterlayer insulating layers 160 and the interlayer sacrificial layers110 by using the predetermined mask pattern as an etching mask. Althoughnot shown in FIG. 5B, a structure including different types of films maybe etched. Thus, inner walls of the plurality of first openings Ta maynot be perpendicular relative to a top surface of the substrate 100. Forexample, widths of the first openings Ta may decrease toward the topsurface of the substrate 100.

The first openings Ta may expose the top surface of the substrate 100 asshown in FIG. 5B. In addition, in the anisotropic etching process,portions of the substrate 100 under the first openings Ta may berecessed to a predetermined depth, as shown in FIG. 5B, due to, e.g., aresult of over-etching.

Referring to FIG. 5C, the channel regions 120 may be formed to uniformlycover inner walls and bottom surfaces of the first openings Ta. Thechannel regions 120 may be formed to a predetermined thickness, e.g., athickness of about 1/50 to about ⅕ of a width of a first opening Ta, byusing atomic layer deposition (ALD) or CVD. The channel regions 120 maydirectly contact the substrate 100 at a bottom of the first openings Taand may be electrically connected to the substrate 100.

Next, each of the first openings Ta may be filled with the buriedinsulating layer 130. The buried insulating layer 130 may be filled notto reach a top surface of the interlayer insulating layer 169, butrather to reach a predetermined height of the interlayer insulatinglayer 169. For example, after a material of the buried insulating layer130 is deposited, an etch-back process may be additionally performed.

In an implementation, before the buried insulating layer 130 is formed,a hydrogen annealing process (for annealing a structure on which thechannel regions 120 are formed in a gas atmosphere including, e.g.,hydrogen or heavy hydrogen) may be further performed. Defects in thechannel regions 120 may be removed using the hydrogen annealing process.

Referring to FIG. 5D, a material used to form the conductive layer 172may be deposited on the buried insulating layer 130. After the materialis deposited, portions of a material of the channel region 120 and amaterial of the conductive layer 172 (which are unnecessary and coverthe interlayer insulating layer 169) may be removed by performing aplanarization process. Accordingly, the conductive layer 172 may beformed on the buried insulating layer 130. For convenience ofexplanation, a portion of the channel region 120 disposed around theconductive layer 172 or a structure or material on the channel regionmay be referred to as the channel extending portion 174. Accordingly,the channel region 120 and the channel extending portion 174 may beformed of the same material. In an implementation, the channel extendingportion 174 may be integrally formed with the conductive layer 172.

Referring to FIG. 5E, a process for removing a part of the interlayerinsulating layer 169 may be performed such that the conductive layer 172and the channel extending portion 174 partially protrude over theinterlayer insulating layer 169. In a cross-sectional view taken along acenter, the conductive layer 172 and the channel extending portion 174may have a first length L1 in a lateral direction. For example, thefirst length L1 may correspond to a diameter of a circle including theconductive layer 172 at its center and surrounded by the channelextending portion 174.

Referring to FIG. 5F, a spacer material 176 a may be formed on theconductive layer 172, the channel extending portion 174, and theinterlayer insulating layer 169. The spacer material 176 a may be aconductive material. The spacer material 176 a may include the samematerial as that of the conductive layer 172 and/or the channelextending portion 174.

Referring to FIG. 5G, the spacer 176 may be formed by partially removingthe spacer material 176 a. The spacer material 176 a may be removed by,e.g., anisotropic etching. Accordingly, the spacer 176 may be formed onthe channel extending portion 174 to surround the channel extendingportion 174. The channel pad 170, including the conductive layer 172,the channel extending portion 174, and the spacer 176, may thus becompletely formed. In an implementation, a bent portion may be formedbetween a bottom surface of the spacer 176 and the channel region 120 orthe channel extending portion 174. After the channel pad 170 is formed,an upper insulating layer 180 may be formed on the interlayer insulatinglayer 169 and the channel pad 170.

The channel pad 170 may have a second length L2 in a lateral direction.The second length L2 may correspond to a diameter of a circle includingthe conductive layer 172 and the channel extending portion 174 at itscenter and surrounded by the spacer 176. The second length L2 may begreater than the first length L1 (described with reference to FIG. 5E),and a landing margin of a bit line contact plug to be formed in asubsequent process may be secured. Also, a decrease of uniformity incontact resistance between memory cell strings and an increase incontact resistance (which may occur when the bit line contact plug isdownwardly longitudinally formed along a side surface of the channelregion 120 due to misalignment) may be reduced and/or prevented.

Referring to FIG. 5H, a second opening Tb (through which the substrate100 is exposed) may be formed. The second opening Tb may extend in they-direction (see FIG. 3). According to the present embodiment, as shownin FIG. 5H, one second opening Tb may be formed between the channelregions 120. However, the embodiments are not limited thereto, andrelative positions of the channel regions 120 and the second opening Tbmay differ.

The second opening Tb may be formed by anisotropically etching the upperinsulating layer 180, the interlayer insulating layers 160, and theinterlayer sacrificial layers 110 (see FIG. 5H). The second opening Tbmay correspond to a region where the common source line 107 is to beformed (extending in a y-direction) in a subsequent process. Theinterlayer sacrificial layers 110 (exposed through the second openingTb) may be removed by an etching process, and thus, a plurality of sideopenings T1 defined between the interlayer insulating layers 160 may beformed. Side walls of the channel regions 120 may be partially exposedthrough the side openings T1.

Referring to FIG. 5I, the gate dielectric film 140 may be formed touniformly cover the channel regions 120, the interlayer insulatinglayers 160, and the substrate 100 exposed through the second opening Tband the side openings T1.

The gate dielectric film 140 may include the tunneling insulating layer142, the charge storage layer 144, and the blocking insulating layer146, which are sequentially stacked from the channel regions 120, asshown in FIG. 4A. The tunneling insulating layer 142, the charge storagelayer 144, and the blocking insulating layer 146 may be formed by, e.g.,ALD, CVD, or physical vapor deposition (PVD).

Next, the second opening Tb and the side openings T1 may be filled witha conductive material 150 a.

Referring to FIG. 5J, a third opening Tc may be formed by partiallyetching the conductive material 150 a. Accordingly, the conductivematerial 150 a may be filled only in the side openings T1 of FIG. 5H, toform the gate electrodes 150. The third opening Tc may be formed byanisotropic etching, and portions of the gate dielectric film 140 formedon top surfaces of the substrate 100 and the upper insulating layer 180may be removed by the anisotropic etching. In an implementation,portions of the gate dielectric films 140 formed on side surfaces of theinterlayer insulating layers 160 may also be removed. Next, the impurityregion 105 may be formed by injecting impurities into the substrate 100through the third opening Tc.

Referring to FIG. 5K, the insulating region 185 and the common sourceline 107 may be formed to fill the third opening Tc. The insulatingregion 185 may be formed by filling an insulating material in the thirdopening Tc and then performing anisotropic etching. In animplementation, the insulating region 185 may be formed of the samematerial as that of the interlayer insulating layers 160. Next, thecommon source line 107 may be formed by depositing a conductive materialand etching the conductive material by using an etch-back process or thelike.

Referring to FIG. 5L, a process of removing the upper insulating layer180 and a portion of the interlayer insulating layer 169 may beperformed to expose a top surface of the channel pad 170. In thisprocess, an amount of the interlayer insulating layer 169 removed is notlimited to a height illustrated in FIG. 5I, and may vary according to aremoval process.

Next, an impurity injection process for the string selection transistorsSST1 and SST2 of the memory cell string (see FIG. 3) formed along thechannel region 120 may be performed. The impurities may include, e.g.,n-type impurities such as phosphorous (P), arsenic (As), or antimony(Sb), or p-type impurities such as boron (B), aluminum (Al), gallium(Ga), or zinc (Zn). In an implementation, the impurity injection processmay be omitted or may be performed in another operation.

Referring to FIG. 5M, a wiring insulating layer 187 may be formed on theinterlayer insulating layer 169, the common source line 107, and thechannel pad 170, and a bit line contact hole CT may be formed throughthe wiring insulating layer 187. The bit line contact hole CT may beformed by photolithography and etching. A bit line contact plug 190 maybe formed by depositing a conductive material in the bit line contacthole CT.

In the present embodiment, due to the channel pad 170 including thespacer 176, a space for forming the bit line contact plug 190 outsidethe channel region 120 may be additionally secured. Accordingly, a poorconnection of the bit line contact plug 190 may be reduced and/orprevented, and resistance at a connection portion may be reduced.

Referring to FIG. 5N, a bit line 195 (for connecting a plurality of thebit line contact plugs 190 arranged in the x-direction) may be formed onthe wiring insulating layer 187 and the bit line contact plugs 190. Thebit line 195 may be formed in a linear shape by, e.g., deposition,photolithography, and etching.

FIG. 6 illustrates a perspective view illustrating a 3D structure ofmemory cell strings of a nonvolatile memory device 2000 according toanother embodiment.

In FIG. 6, some elements constituting the memory cell string 11 of FIG.1 are not shown. For example, the bit lines BL1 through BLm of thememory cell string 11 are not shown. In FIG. 6, the same elements asthose in FIG. 3 are denoted by the same reference numerals, and thus, arepeated detailed explanation thereof is omitted.

Referring to FIG. 6, the nonvolatile memory device 2000 may include thechannel regions 120 disposed on the substrate 100 and a plurality ofmemory cell strings 11 (see FIG. 1) along side walls of the channelregions 120. In FIG. 6, the channel regions 120 are disposed at a higherdensity than in FIG. 3. As shown in FIG. 6, the memory cell strings 11or 11A (see FIGS. 1 and 2) extending in the z-direction from thesubstrate 100 may be arranged along the side walls of the channelregions 120. Each of the memory cell strings 11 or 11A may include twoground selection transistors GST1 and GST2, a plurality of memory cellsMC1, MC2, MC3, and MC4, and two string selection transistors SST1 andSST2.

The impurity regions 105 may be arranged adjacent to the main surface ofthe substrate 100 to extend in the y-direction and to be spaced apart inthe x-direction. Unlike in FIG. 3, the common source line CSL of FIGS. 1and 2 may be connected to the impurity regions 105 on another region(not shown). The insulating regions 185 may be formed on the impurityregions 105.

The channel pad 170 may cover a top surface of the buried insulatinglayer 130 and may be electrically connected to each of the channelregions 120. The channel pad 170 may include the conductive layer 172(on the top surface of the buried insulating layer 130), the channelextending portion 174 (on the channel region 120 or formed when thechannel region 120 extends around the conductive layer 172), and thespacer 176 (disposed around the channel extending portion 174). Adistance between the substrate 100 and a bottom surface of the spacer176 may be greater than a distance between the substrate 100 and abottom surface of the conductive layer 172. The channel pad 170 mayinclude a conductive material, e.g., polysilicon or a metal. Theconductive layer 172, the channel extending portion 174, and the spacer176 may include the same material or different materials. In animplementation, only the conductive layer 172 and the channel extendingportion 174 may be formed of the same material.

A bit line contact plug (not shown) may be connected to the channel pad170. The channel pad 170 may act as drain regions of the stringselection transistors SST1 and SST2. Due to the spacer 176, an area of aregion to which the bit line contact plug is connected may have a secondarea S2, which may be greater than a first area S1 (e.g., a sectionalarea of the conductive layer 172 and the channel extending portion 174).

An insulating spacer 183 may be disposed around the spacer 176 of thechannel pad 170. The insulating spacer 183 may include an insulatingmaterial. The insulating material may have an etch selectivity withrespect to the interlayer insulating layers 160 and the insulatingregion 185. For example, the insulating material may include siliconnitride. A third area S3, e.g., of the insulating spacer 183 and thechannel pad 170, may be greater than the second area S2. During anetching process for forming a bit line contact plug (not shown) on thechannel pad 170, an etching margin may be secured due to the insulatingspacer 183, which will be explained in detail below with reference toFIGS. 7A through 7G.

In the nonvolatile memory device 2000 having a vertical structure ofFIG. 6, the channel pad 170 and the insulating spacer 183 (to which thebit line contact plug for connecting the channel region 120 and a bitline is connected) may have an area greater than a sectional area, e.g.,an area encompassed by, the channel region 120. Accordingly, althoughthe size of the channel region 120 may decrease as the nonvolatilememory device 2000 is minimized, the bit line contact plug may be stablyformed.

FIGS. 7A through 7G illustrate cross-sectional views of stages in amethod of manufacturing the nonvolatile memory device 2000 of FIG. 6,when seen in the y-direction.

In FIGS. 7A through 7G, the same elements as those in FIGS. 5A through5N are denoted by the same reference numerals, and thus, a repeateddetailed explanation thereof is omitted.

Referring to FIG. 7A, the same processes as described with reference toFIGS. 5A through 5D may be sequentially performed.

The interlayer sacrificial layers 111 through 118 (which arecollectively referred to as the interlayer sacrificial layers 110) andthe plurality of interlayer insulating layers 161 through 169 (which arecollectively referred to as the interlayer insulating layers 160) may bealternately stacked on the substrate 100. The interlayer sacrificiallayers 110 may be formed of a material having an etch selectivity withrespect to the interlayer insulating layers 160.

Next, first openings Ta may be formed through the alternately stackedinterlayer insulating layers 160 and interlayer sacrificial layers 110.The first openings Ta may be holes having a depth in the z-direction.Next, the channel regions 120 may be formed to uniformly cover innerwalls and bottom surfaces of the first openings Ta, and the buriedinsulating layer 130 may be filled in each of the first openings Ta. Theburied insulating layer 130 may be filled not to reach a top surface ofthe interlayer insulating layer 169, but rather to reach to apredetermined height of the interlayer insulating layer 169.

Next, a material used to form the conductive layer 172 may be depositedon the buried insulating layer 130. After the deposition, portions of amaterial of the channel region 120 and a material of the conductivelayer 172 (which portions are unnecessary and cover the interlayerinsulating layer 169) may be removed by performing a planarizationprocess. Accordingly, the conductive layer 172 may be formed on theburied insulating layer 130. For convenience of explanation, a structureor material on the channel region or a portion of the channel region 120disposed around the conductive layer 172 may be referred to as thechannel extending portion 174. For example, the channel extendingportion 174 may extend from a top of the channel region 120. In animplementation, the channel region 120 and the channel extending portion174 may be formed of the same material. However, in anotherimplementation, the channel extending portion 174 may include a materialdifferent from that of the channel region 120.

Referring to FIG. 7B, similar processes as those described withreference to FIGS. 5H through 5J may be sequentially performed.

The second opening Tb (through which the substrate 100 is exposed) maybe formed. The interlayer sacrificial layers 110 (exposed through thesecond opening Tb) may be removed by etching, and thus, the plurality ofside openings T1 (see FIG. 5H) defined between the interlayer insulatinglayers 160 may be formed.

Next, the gate dielectric film 140 may be formed to uniformly cover thechannel regions 120, the interlayer insulating layers 160, and thesubstrate 100 exposed through the second opening Tb and the sideopenings T1. The gate dielectric film 140 may include the tunnelinginsulating layer 142, the charge storage layer 144, and the blockinginsulating layer 146, which may be sequentially stacked from the channelregions 120, as shown in FIG. 4A.

Next, the gate electrodes 150 may be formed in the second opening Tb andthe side openings T1. The gate electrodes 150 may be formed bydepositing a conductive material (not shown), forming a third opening(not shown) at a same position as that of the second openings Tb, andpartially removing the conductive material. Next, the impurity regions105 may be formed by injecting impurities into the substrate 100 throughthe third opening (not shown).

Next, an insulating material 185 a filled in the third opening Tc may beformed. The insulating material 185 a may be a same material as that ofthe interlayer insulating layers 160. The insulating material 185 a maybe formed to be filled in the third opening Tc and to cover theinterlayer insulating layer 169, the conductive layer 172, and thechannel extending portion 174.

Referring to FIG. 7C, a process for removing a portion of the insulatingmaterial 185 a and a portion of the interlayer insulating layer 169 suchthat the conductive layer 172 and the channel extending portion 174protrude over the interlayer insulating layer 169 may be performed. In across-sectional view taken along a center, the conductive layer 172 andthe channel extending portion 174 may have a first length L1 in alateral direction. For example, the first length L1 may correspond to adiameter of a circle including the conductive layer 172 at its centerand surrounded by the channel extending portion 174. Due to thisprocess, the insulating regions 185 may be formed on the impurityregions 105. In this process, an amount or degree of the interlayerinsulating layer 169 removed may not be limited to a height illustratedin FIG. 7C, and may vary according to a removal process.

Next, an impurity injection process for channels of the string selectiontransistors SST1 and SST2 (see FIG. 3) of the memory cell strings formedalong the channel regions 120 may be performed. In an implementation,the impurity injection process may be omitted or may be performed inanother operation.

Referring to FIG. 7D, similar processes as those described withreference to FIGS. 5F and 5G may be sequentially performed.

The spacer 176 may be formed on the conductive layer 172, the channelextending portion 174, and the interlayer insulating layer 169. Thespacer 176 may be formed by depositing a conductive material (notshown), and partially removing the conductive material by, e.g.,anisotropic etching. The spacer 176 may include the same material asthat of the conductive layer 172 and/or the channel extending portion174.

The spacer 176 may be formed to surround an upper portion of the channelextending portion 174. Thus, the channel pad 170 (including theconductive layer 172, the channel extending portion 174, and the spacer176) may be completely formed. The channel pad 170 may have a secondlength L2 in a lateral direction. The second length L2 may correspond toa diameter of a circle including the conductive layer 172 and thechannel extending portion 174 at its center and surrounded by the spacer176. The second length L2 may be greater than the first length L1described with reference to FIG. 7C, and thus, a landing margin of a bitline contact plug (to be formed in a subsequent process) may be secured.

According to the method of manufacturing the nonvolatile memory device2000, the spacer 176 may be formed after the gate electrodes 150 areformed, unlike in the method described with reference to FIGS. 5Athrough 5N.

Referring to FIG. 7E, an insulating material 183 a may be deposited onthe interlayer insulating layer 169, the channel pad 170, and theinsulating region 185. The insulating material 183 a may be a materialthat has an etch selectivity with respect to the interlayer insulatinglayer 169 and the insulating region 185. In an implementation, theinsulating material 183 a may include, e.g., silicon nitride or siliconcarbide.

Referring to FIG. 7F, the insulating spacer 183 may be formed around thespacer 176 by partially removing the insulating material 183 a. Adifference between heights of the insulating spacer 183 and the spacer176 is not limited to a height illustrated in FIG. 7F, and may vary invarious ways. A lateral length of the insulating spacer 183 includingthe channel pad 170 at its center may be a third length L3. The thirdlength L3 may be greater than the second length L2 described withreference to FIG. 7D, and thus, a process margin of a bit line contact(to be formed in a subsequent process) may be secured. For example, abit line contact may be prevented from being downwardly longitudinallyformed along side surface of the channel region 120 due to misalignment.

Referring to FIG. 7G, the wiring insulating layer 187 may be formed onthe interlayer insulating layer 169 and the channel pad 170, and the bitline contact plug 190 may be formed through the wiring insulating layer187. The bit line contact plug 190 may be formed by forming a bit linecontact hole CT by photolithography and etching, and depositing aconductive material.

The wiring insulating layer 187 may include the same material as that ofthe interlayer insulating layer 169. Also, the wiring insulating layer187 may include a material that has an etch selectivity with respect tothe insulating spacer 183. Accordingly, when an etching process forforming the bit line contact hole CT is performed, even when the bitline contact hole CT is formed by a predetermined width outside thespacer 176, the bit line contact hole CT may be prevented from beingformed by etching due to the insulating spacer 183.

Next, the bit line 195 (for connecting a plurality of the bit linecontact plugs 190 arranged in the x-direction) may be formed on thewiring insulating layer 187 and the bit line contact plugs 190. The bitline 195 may be formed in a linear shape by photolithography andetching.

FIG. 8 illustrates a perspective view of a 3D structure of memory cellstrings of a nonvolatile memory device 3000 according to yet anotherembodiment.

In FIG. 8, some elements constituting the memory cell string 11 of FIG.1 may not be shown. For example, the bit lines BL1 through BLm of thememory cell string 11 are not shown. In FIG. 8, the same elements asthose in FIGS. 3 and 6 are denoted by the same reference numerals, andthus, a repeated detailed explanation thereof is omitted.

Referring to FIG. 8, the nonvolatile memory device 3000 may includechannel regions 120 disposed on the substrate 100, and a plurality ofmemory cell strings disposed on side walls of the channel regions 120.As shown in FIG. 8, the memory cell strings 11 or 11A (see FIGS. 1 and2) extending in the z-direction from the substrate 100 may be arrangedalong the side walls of the channel regions 120. Each of the memory cellstrings 11 or 11A may include two ground selection transistors GST1 andGST2, a plurality of memory cells MC1, MC2, MC3, and MC4, and two stringselection transistors SST1 and SST2.

The channel pad 170 may be formed to cover a top surface of the buriedinsulating layer 130 and to be electrically connected to respective onesof the channel regions 120. The channel pad 170 may include theconductive layer 172 (disposed on the top surface of the buriedinsulating layer 130), the channel extending portion 174 (e.g., astructure or material on the channel region 120 or formed when thechannel region 120 extends around the conductive layer 172), and a coverportion 178 (disposed on top surfaces of the conductive layer 172 andthe channel extending portion 174, e.g., overlying the conductive layer172 and the channel extending portion 174). A height of the conductivelayer 172 may not be limited to a height illustrated in FIG. 8, and mayvary on a side surface of the interlayer insulating layer 169. A bitline contact plug (not shown) may be connected to the channel pad 170,and the channel pad 170 may act as drain regions of the string selectiontransistors SST1 and SST2. Due to the cover portion 178, an area of aregion to which the bit line contact plug is connected may berepresented by a second area S2, which may be greater than a first areaSi (e.g., a sectional area of the channel extending portion 174 togetherwith the conductive layer 172).

The channel pad 170 may include a conductive material, e.g., polysiliconor a metal. The conductive layer 172, the channel extending portion 174,and the cover portion 178 may include the same material or differentmaterials. In an implementation, only the conductive layer 172 and thechannel region 174 may be formed of the same material.

In the nonvolatile memory device 3000 having a vertical structure ofFIG. 8, the channel pad 170 (to which the bit line contact plug forconnecting the channel region 120 and a bit line is connected) may beformed to have an area greater than that of each of the channel regions120. Accordingly, although a size of the channel region 120 may decreaseas the nonvolatile memory device 3000 is minimized, the bit line contactplug may be stably formed.

FIGS. 9A through 9C illustrate cross-sectional views showing stages in amethod of manufacturing the nonvolatile memory device 3000 of FIG. 8,when seen in the y-direction.

Referring to FIG. 9A, the same processes as those described withreference to FIGS. 5A through 5D may be sequentially performed, andthus, a repeated detailed description thereof is omitted.

The plurality of interlayer sacrificial layers 111 through 118 (whichare collectively referred to as the interlayer sacrificial layers 110)and the plurality of interlayer insulating layers 161 through 169 (whichare collectively referred to as the interlayer insulating layers 160)may be alternately stacked on the substrate 100. The channel region 120and the buried insulating layer 130 may be formed in each of the firstopenings Ta.

Next, the conductive layer 172 may be formed on the buried insulatinglayer 130. For convenience of explanation, a structure or material onthe channel region or a portion of the channel region 120 disposedaround the conductive layer 172 may be referred to as the channelextending portion 174. In an implementation, the conductive layer 172and the channel extending portion 174 may be integrally formed.

Next, a conductive material 178 a may be deposited on the interlayerinsulating layer 169, the conductive layer 172, and the channelextending portion 174. The conductive material 187 a may be the samematerial as that of the channel region 120 and the channel extendingportion 174. In an implementation, the conductive material 178 a may bedifferent from that of the channel extending portion 174 and the channelregion 120.

Referring to FIG. 9B, a process of patterning the conductive material178 a may be performed. The patterning process may include patterning aphotoresist layer (not shown) on the conductive material 178 a bylithography and etching an exposed portion of the conductive material178 a. Accordingly, the cover portion 178 (which covers top surfaces ofthe conductive layer 172 and the channel extending portion 174) may beformed, and the channel pad 170, (including the conductive layer 172,the channel extending portion 174, and the cover portion 178) may beformed. The cover portion 178 may have, e.g., a cylindrical shape or apolygonal pillar shape.

In a cross-sectional view taken along a center, the conductive layer 172and the channel extending portion 174 may have a first length L1 in alateral direction. For example, the first length L1 may correspond to adiameter of a circle including the conductive layer 172 at its centerand surrounded by the channel extending portion 174. In across-sectional view taken along the center of the cover portion 178,the cover portion 178 may have a second length L2, and the second lengthL2 may be greater than the first length L1. In an implementation, a bentportion may be formed outside the channel extending portion 174 at aportion to which the channel extending portion 174 and the cover portion178 are connected.

Referring to FIG. 9C, similar processes as those described withreference to FIGS. 5H through 5N may be sequentially performed, andthus, a repeated detailed explanation thereof is omitted.

After the gate electrodes 150 are formed, the wiring insulating layer187 may be formed on the interlayer insulating layer 169 and the channelpad 170. Next, the bit line contact plug 190 may be formed on the coverportion 178 through the wiring insulating layer 187.

According to the present embodiment, the channel pad 170 may include thecover portion 178. Thus, a space for forming the bit line contact plug190 outside the channel region 120 may be additionally secured.Accordingly, poor connection of the bit line contact plug 190 may bereduced and/or prevented, and resistance at a connection portion may bereduced.

Next, the bit line 195 for connecting the bit line contact plugs 190arranged in the x-direction may be formed on the wiring insulating layer187 and the bit line contact plugs 190. The bit line 195 may be formedin a linear shape by photolithography and etching.

FIG. 10 illustrates a block diagram of a nonvolatile memory device 700according to an embodiment.

Referring to FIG. 10, in the nonvolatile memory device 700, a NANDmemory cell array 750 may be connected to a core circuit unit 770. Forexample, the NAND memory cell array 750 may include any one of thenonvolatile memory devices 1000, 2000, and 3000 of FIGS. 3, 6, and 8.The core circuit unit 770 may include, e.g., a control logic 771, a rowdecoder 772, a column decoder 773, a sense amplifier 774, and a pagebuffer 775.

The control logic 771 may communicate with the row decoder 772, thecolumn decoder 773, and the page buffer 775. The row decoder 772 maycommunicate with the NAND memory cell array 750 via a plurality ofstring selection lines SSL, a plurality of word lines WL, and aplurality of ground selection lines GSL. The column decoder 773 maycommunicate with the NAND memory cell array 750 via a plurality of bitlines BL. The sense amplifier 774 may be connected to the column decoder773 when a signal is output from the NAND memory cell array 750, and maynot be connected to the column decoder 773 when a signal is transmittedto the NAND memory cell array 750.

For example, the control logic 771 may transmit a row address signal tothe row decoder 772, and the row decoder 772 may decode the row addresssignal and transmit the same to the NAND memory cell array 750 via thestring selection lines SSL, the word lines WL, and the ground selectionlines GSL. The control logic 771 may transmit a column address signal tothe column decoder 773 or the page buffer 775, and the column decoder773 may decode the column address signal and transmit the same to theNAND memory cell array 750 via the plurality of bit lines BL. A signalof the NAND memory cell array 750 may be transmitted to the senseamplifier 774 via the column decoder 773, may be amplified by the senseamplifier 774, and then may be transmitted to the control logic 771through the page buffer 775.

By way of summation and review, a nonvolatile memory device having avertical structure may include a bit line contact plug for connecting abit line and a channel region. In one type of nonvolatile memory devicehaving a vertical structure, a channel pad having the same size as thatof a channel region may be formed on the channel region having avertical hole shape in order to be connected to a bit line contact plug.

However, as semiconductor devices are more highly integrated and sizesof channel regions are minimized, a margin of a bit line contact plugmay decrease. Also, if a bit line contact plug is formed at a sidesurface of a channel region along the channel region, a contact area maynot be constant due to misalignments.

The embodiments provide a nonvolatile memory device having a verticalstructure with high integration density and high reliability, e.g.,reliable connections having a constant contact area between a bit linecontact plug and a channel region, thereby avoiding poor RCdistribution.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

1. A nonvolatile memory device having a vertical structure, thenonvolatile memory device comprising: a channel region that verticallyextends from a substrate; gate electrodes on the substrate, the gateelectrodes being disposed along an outer side wall of the channel regionand spaced apart from one another; and a channel pad that extends fromone side of the channel region to an outside of the channel region, thechannel pad covering a top surface of the channel region.
 2. Thenonvolatile memory device as claimed in claim 1, wherein the channel padincludes: a channel extending portion vertically extending on thechannel region, and a spacer on an outer circumferential surface of thechannel extending portion.
 3. The nonvolatile memory device as claimedin claim 2, further comprising a buried insulating layer at a center ofthe channel region, wherein the channel pad further includes aconductive layer on a top surface of the buried insulating layer, theconductive layer filling in the channel extending portion.
 4. Thenonvolatile memory device as claimed in claim 3, wherein a distancebetween the substrate and a bottom surface of the conductive layer isless than a distance between the substrate and a bottom surface of thespacer.
 5. The nonvolatile memory device as claimed in claim 2, whereinthe spacer forms a bent portion at a boundary with an outer side wall ofthe channel extending portion or the channel region.
 6. The nonvolatilememory device as claimed in claim 1, wherein an area of a top surface ofthe channel pad is greater than an area of the top surface of thechannel region.
 7. The nonvolatile memory device as claimed in claim 1,further comprising a bit line contact plug on the channel pad, the bitline contact plug being connected to a bit line.
 8. The nonvolatilememory device as claimed in claim 1, further comprising an insulatingspacer on a side surface of the channel pad.
 9. The nonvolatile memorydevice as claimed in claim 1, wherein the channel pad includes: achannel extending portion vertically extending on the channel region,and a cover portion on the channel extending portion, the cover portionhaving an area greater than an area of the channel extending portion.10-15. (canceled)
 16. A nonvolatile memory device having a verticalstructure, the nonvolatile memory device comprising: a channel regionthat vertically extends from a substrate; gate electrodes on thesubstrate, the gate electrodes being disposed along an outer side wallof the channel region and spaced apart from one another; and aconductive channel pad on and electrically connected to the channelregion, wherein: the channel pad covers a top surface of the channelregion, and an area of a top surface of the channel pad is greater thanan area of a top surface of the channel region.
 17. The nonvolatilememory device as claimed in claim 16, wherein the channel pad includes aconductive channel extending portion overlying the channel region, aconductive layer encompassed by the channel extending portion, and aconductive spacer on an outer circumferential surface of the channelextending portion.
 18. The nonvolatile memory device as claimed in claim17, further comprising an insulating spacer on an outer circumferentialsurface of the channel pad.
 19. The nonvolatile memory device as claimedin claim 16, wherein the channel pad includes a conductive channelextending portion overlying the channel region, a conductive layerencompassed by the channel extending portion, and a conductive coverportion overlying the channel extending portion and the conductivelayer, an area of a top surface of the cover portion being greater thanan area of top surfaces of the channel extending portion and theconductive layer.
 20. The nonvolatile memory device as claimed in claim16, further comprising a bit line contact plug on and electricallyconnected to the channel pad, the bit line contact plug beingelectrically connected to a bit line.